dlopen() returns undefined symbol for library w/ RTLD_LAZY

[Steve Lawler]

I am using gcc-2.95.2 and glibc-2.2 (sadly, I am 
using RH7.0's glibc-2.2) w/ Linux 2.4.2.  Now perhaps I don't know how 
dlopen() is supposed to work, but....
 
If I try to dlopen() a shared library with 
RTLD_LAZY, and the library in question references an external symbol that is not 
defined in a system library (like libc or something), dlopen() fails and dlerror 
will print: "X.so: undefined symbol: FOO".
 
For example:
 
lib1.c:
#include <stdio.h>
 
extern int x(void);
 
void lib1_func(void) { printf("x = %d\n", x); 
}
-------------------
 
test.c:
#include <stdio.h>
 
int x(void) { return 99; }
 
int main(void) {
    void *h;
    h = dlopen("./lib1.so", 
RTLD_LAZY);
    if (!h) { printf("%s\n", 
dlerror()); }
    if (h) dlclose(h);
    return 0;
}
--------------------
 
$ cc -c lib1.c
$ cc -c test.c
$ ld -shared lib1.o -o lib1.so
$ cc test.o -o test -ldl
$ ./test
./lib1.so: undefined symbol: x
 
 
I thought that RTLD_LAZY forced symbols to be evaluated as 
they are loaded from the shared object; thus dlopen() would not try to load 
all of ./lib1.so's symbols immediately upon opening; that would be deferred 
until, say, I tried to load lib1_func with dlsym(), at which point it would try 
to resolve x() (and, I would hope, it would be resolved to the 'x' found in 
test.o but... ?) 
 
Also I am wondering why I don't get a message like 
"./lib1.so: undefined symbol: printf"
 
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